Childhood anxiety disorders are arguably the most prevalent emotional disorders of childhood and can negatively impact children's school and interpersonal functioning (Keller et al., 1992; Silverman & Ginsburg, 1998). The proposed research is targeted at a critical gap in understanding the cognitive developmental origins of anxiety disorders. That is, the research is aimed at investigating the role of children's reasoning about anxiety sensations. Anxiety sensitivity refers to beliefs that anxiety related sensations (such as feeling shaky, increased heart rate, trembling, shortness of breath) have severe negative social, psychological, or physical consequences. A growing body of evidence implicates anxiety sensitivity as a risk factor for panic as well as other anxiety disorders in adult and adolescent samples (e.g., Hayward, Killen, Kraemer & Taylor, 2000; Mailer & Reiss, 1992; Schmidt, Lerew, & Jackson, 1997; Schmidt, Lerew, and Jackson, 1999). Given the accumulating evidence for a role of anxiety sensitivity in the etiology of panic it is important to better understand the developmental phenomenology of anxiety sensitivity because the utility of existing assessments has been questioned in children under age 12. A clearer understanding of the reasoning that children use in interpreting anxiety sensations and the changes that occur developmentally in that reasoning can help maximize the utility of assessing anxiety sensitivity and facilitate the use of anxiety sensitivity theory for understanding childhood anxiety disorders. The first specific aim of the proposed research is the development of an instrument that will assess children's reasoning about anxiety sensations. The second aim is the identification of the types of reasons that children use to evaluate anxiety symptoms (e.g., does their reasoning involve attributing severe negative social, psychological, or physical consequences to anxiety, sensations as adults do). The third and final aim is to explore possible developmental differences in children's reasoning about anxiety sensations.